Field of the Invention
Embodiments described herein relate generally to a multiple charged particle beam lithography apparatus and a multiple charged particle beam pattern writing method and, for example, relate to a method of correcting a positional displacement or a dimensional displacement of a pattern caused by a positional displacement of a beam in multiple beams pattern writing by modulating a dose.
Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process for exclusively generating a pattern in semiconductor manufacturing processes. In recent years, with an increase in integration density of an LSI, a circuit line width required for semiconductor devices is getting smaller year by year. An electron beam pattern writing technique has inherently superior resolution and a mask pattern is written to mask blanks using an electron beam.
For example, a lithography apparatus using multiple beams is known. Compared with a case in which one electron beam is used, many beams can be emitted at a time by using multiple beams so that throughput can be improved significantly. In such a lithography apparatus of multiple beams mode, for example, an electron beam emitted from an electron gun assembly is passed through a mask having a plurality of holes to form multiple beams, each beam is subjected to blanking control, and each beam that is not shielded is reduced by an optical system to reduce a mask image and deflected by a deflector before being shot at a predetermined position on a target object.
Here, in multiple beams pattern writing, a positional displacement of beam could arise due to a distortion of the optical system, a displacement of an aperture plate array to form multiple beams from design values, and/or the Coulomb effect. If a positional displacement of a beam constituting multiple beams arises, a problem that a written pattern also has a positional displacement or a dimensional displacement arises. Therefore, it is desirable to correct positional displacement and dimensional displacement of a pattern formed with a positionally-displaced beam being irradiated. For a positional displacement caused by an optical strain, for example, operating a shot position containing a distortion portion for a positional displacement caused by an optical strain to adjust the dose of a beam with which the shot position is irradiated in accordance with pattern area density positioned in a region constituted by assuming the shot position containing the distortion portion is proposed (see Published Unexamined Japanese Patent Application No. 2014-007379 (JP-A-2014-007379), for example).
However, a sufficiently effective technique to correct positional displacement and dimensional displacement of a pattern formed by being irradiated with a positionally-displaced beam is not yet established.